This invention relates to endoscopic catheters, and more particularly relates to catheters equipped to accomplish a therapeutic procedure at an internal site such as a gastrointestinal site.
Endoscopic catheters are employed for accomplishing a variety of internal therapeutic procedures, for example, for enabling injection therapy at a site of bleeding in the digestive system. Typically, a catheter equipped for such injection therapy includes a needle at the distal end of an injection sheath through which liquid therapeutic injection media is channeled to the needle. An outer sheath over the injection sheath is also typically included to provide both a passageway for irrigation fluid around the needle and a protective encasement for the needle as the distal end of the catheter is moved to the therapy site. Endoscopic catheters equipped for other applications, e.g., delivery of a mechanical vasoconstrictor to an internal site, similarly generally include a mechanical feature at the distal end of an inner sheath that is encased in an outer sheath. Many endoscopic therapeutic procedures are directed to deep internal sites that require an appropriately equipped catheter to be of substantial length, e.g., greater than about one or two meters, to reach the site of interest through, e.g., an endoscope, and further require flexibility in the catheter sheaths for ease of conformance to curves in internal cavities as the catheter is advanced to the intended internal site.
Conventionally, the position of the distal end of an inner catheter sheath and its distal end element, e.g., a needle, is controlled with respect to the outer catheter sheath by way of a remote hand-operable control mechanism at the catheter proximal end opposite the distal end element. For example, as the needle on a catheter is advanced to its intended site, either the injection sheath or outer catheter sheath is typically controlled by hand outside the endoscope to shield the needle from the internal cavity; once the intended site is reached, the needle is then forwardly advanced out the distal end of the outer sheath.
However, the long length and flexibility generally required of catheter sheaths result in only imprecise control of the distal ends of the sheaths using a hand-operable proximal control, however. In particular, it is difficult to achieve precise positioning of the distal end of one sheath with respect to the other using a control mechanism located remotely, at least one meter away, at the opposite, proximal ends of the sheaths, and this limitation is exacerbated by the unpredictable friction between and along the flexible sheaths. Yet the nature of endoscopic therapies typically requires that the distal ends of the sheaths not be rigidly fixed with respect to each other. As a result, the effectiveness of endoscopic therapeutic procedures can be compromised due to ineffective position control of catheter sheath distal ends.
The invention provides an endoscopic catheter position control that enables precise control of distal catheter sheath ends relative to each other while accommodating the long length and flexibility of typical catheters and proximal, remote hand-operable control mechanisms.
Accordingly, in one aspect, the invention provides a catheter assembly that includes an elongated flexible tubular sheath having a distal end and a proximal end. A distal end member is internal to the sheath; this end member is reciprocally axially moveable relative to the sheath distal end between a retracted position that is proximal of the sheath distal end and an extended position in which the end member protrudes beyond the sheath distal end. An elongated end member interconnector is provided, with a distal end of the interconnector being connected to the end member and a proximal end of the interconnector being connected to a position actuator for axially reciprocating the end member relative to the distal end of the sheath. A distal end position controller is located at a point along the sheath to cooperate with the interconnector in limiting the extent of axial retraction of the end member relative to the sheath distal end. A flow channel that extends axially through the end position controller is internal to the sheath and external to the interconnector.
With this catheter assembly configuration, irrigation or other fluid can be delivered through the outer sheath in the conventional manner with the inner interconnector and distal end member in a fully-retracted position. Unobstruction of the outer sheath fluid communication path provides a superior advantage in that it does not require the addition of an auxiliary or additional fluid communication path beyond the conventional path.
In one embodiment provided by the invention, the end position controller is located at a relatively distal position along the tubular sheath and is embodied as at least one indentation in the sheath that has an inner diameter that is less than an outer diameter of the interconnector at least one point along the interconnector. Here the interconnector can include a connector that has an outer diameter that is greater than the inner diameter of the indentation. The connector enables connection of the distal end member to the interconnector. Preferably, a plurality of indentations are provided in the sheath, with each indentation being circumferentially separated from adjacent indentations by a flow channel.
In other embodiments, the tubular sheath is a polytetrafluoroethylene sheath and further, the interconnector is a flexible tubular inner sheath. Here the end member can be embodied as a needle cannula connected to the inner sheath, with a connector connecting the needle cannula to the inner sheath.
In another aspect, the invention provides an injection catheter assembly including an elongated, flexible, tubular sheath having a distal end and a proximal end. A needle cannula is internal to the sheath and includes a needle tip that is reciprocally axially moveable relative to the distal end of the sheath between a retracted position in which the sheath covers the needle tip and an extended position in which the needle tip protrudes beyond the sheath distal end. An elongated flexible tube internal to the sheath is connected at its distal end by a needle connector to the needle cannula, and is connected at its proximal end to a position actuator for axially reciprocating the needle tip relative to the sheath distal end. A distal end position controller is located at a point along the sheath to cooperate with the needle connector in limiting the extent of axial retraction of the needle tip relative to the sheath distal end.
Preferably, the tubular sheath and the flexible tube each provide a continuous fluid transmission path between the corresponding sheath and tube distal and proximal ends. The end position controller is in one embodiment located at a relatively distal position along the sheath, preferably corresponding to a fully-retracted needle tip position.
In a further aspect, the invention provides a syringe having a barrel with a distal end and a proximal end. A needle cannula is located internal to the barrel and is reciprocally axially moveable relative to the barrel distal end between a retracted position proximal of the barrel distal end in which the barrel covers the needle tip and an extended position in which the needle tip protrudes beyond the barrel distal end. A needle plunger rod is internal to the barrel; the rod is connected at its distal end to the needle cannula and is connected at its proximal end to a position actuator for axially reciprocating the needle tip relative to the barrel distal end. A distal end position controller is located at a point along the barrel to cooperate with the plunger rod in limiting the extent of axial retraction of the needle tip relative to the barrel distal end. The location of the controller corresponds to the fully retracted needle tip position. Preferably, the plunger rod is connected to the needle by a needle connector, and the position controller preferably is embodied as at least one indentation in the barrel at a point at which retraction of the needle connector to the indentation indicates that the needle cannula tip is fully retracted within the barrel.
The position control of the invention facilitates effective and reliable hand-operable remote control of catheter and syringe distal end members with a mechanism that can be located locally to the distal end but that does not itself require external control; i.e., it provides automatic position control. This control can be applied to a wide range of catheter and syringe configurations where only remote active control of distal end elements can be relied upon during a therapeutic procedure. Other features and advantages of the invention will be apparent from the claims, and from the following description and accompanying drawings.